
public class square 
{
	Point2D a;
	Point2D b;
	public square(Point2D a, Point2D b) 
	{		 
		this.a = a;
		this.b = b;
	}
	public double arie()
	{
		return (Point2D.distanta(a,b)*Point2D.distanta(a,b))/2;
	
	}
	public static void main(String[] argv)
	{
		square p=new square(new Point2D(1,2),new Point2D(2,1));
		System.out.println(p.arie());
	}

}
